Hello there! I'm Dr. Vinifera, or "Vinny" for short. Ask me your toughest wine questions, from the technical aspects of winemaking to the fine points of etiquette. I hope you find my answers educational and even amusing. Looking for a particular answer? Check my archive and my FAQs. You can also follow me on Twitter: @AskDrVinny.

Dear Dr. Vinny,

I have a question about label terms. I found a bottle of Cabernet Sauvignon in Costco under their brand “Kirkland” using Napa County instead of Napa Valley. Could you please tell me what “Napa County” means?

—Xiaomeng Y., Beijing

Dear Xiaomeng,

Most of the time when you see a bottle of wine from California or elsewhere in the United States, the appellation (the identifying name of the place where the grapes are grown) is what’s called an American Viticultural Area, or AVA. These AVAs—names like Napa Valley or Sta. Rita Hills or Mendocino Ridge—are defined after the government determines that they are distinguishable geographic locations. It’s a long, costly and sometimes contentious process to prove that an AVA has a distinguishable boundary, unique soils and climates, and historical relevance.

Wines are also allowed to be identified by state or county boundaries. Sometimes you’ll see a wine labeled simply as “California,” and that often means that the grapes for that bottling were blended from different sources all over the state. California also has 58 counties, which tend to be larger areas than most AVAs and can also be used on a label. You typically see counties listed only if they’re associated with winegrowing regions, like Napa County or Sonoma County.

Keep in mind that AVAs can overlap—some AVAs are located within other AVAs, like how Oakville is a sub-region of Napa Valley. Furthermore, within legal limits, it’s up to a winery how specifically it wants to identify its appellation. Sometimes a winery will put a very specific appellation on the label because it carries more cachet. Other wineries might use a broader appellation, which gives them flexibility if they might get their grapes from different sources each year, but don’t want to redesign the label each vintage.

So, getting back to your question, Napa Valley refers to a specific part of Napa County, a strip of land bordered by two mountain ranges, that’s a little less than a third of the size of the entire county. So if a wine says “Napa County,” it could mean the grapes come from Napa Valley, or from parts of Napa County that aren’t in the definition of the Napa Valley AVA, or from some combination of the two.

Learn from the experts and get the most out of each sip. Take one of our online courses or take them all—from the ABCs of Tasting to in-depth seminars on Food Pairing, California Cabernet, Bordeaux, Tuscany, Sensory Evaluation and more.